Film-Tech Forum ARCHIVE: JBL 3677 4648

This is topic JBL 3677 4648 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=009926

Posted by David Alexander B (Member # 4862) on 06-04-2009, 03:06 AM:

good morning
i have at home this combination (room is 430X260X900cm)
LR: 3677
C: 3677+4648 (active biam current crossover DBX set at 140hz)
SUR 8340
SUBS: 4645Cx2
anyone has an opinion at best crossover point you'd use for the Center? let it's sub 15s go to 500hz as they are cut in the big models like 4670 or 4675C ? it's an unconventional Center I concede. (3677 on top of 4648).
thanks.

Posted by Demetris Thoupis (Member # 833) on 06-04-2009, 11:09 AM:

For the 3677 the Frequency Range is 40 Hz to 20 kHz (-10 dB) and for the 4648 the Frequency Range is 30 Hz - 1.8 kHz (-10 dB). I would prefer to keep the 4648 working to it's full capacity thus putting the crossover frequency at 1.8 kHz because the 3677 is not as efficient as the 4648 is the mid/lows. 140hz is way low I believe as you are utilising the 4648 as a subwoofer only while it is capable of mid frequencies as well.
Demetris

Posted by David Alexander B (Member # 4862) on 06-04-2009, 01:40 PM:

hi
thanks for the comment
the issue is two fold:
1. the center channel sub is on the floor. one woofer below the screen. you can "feel" the low fq from the bottom
2. also a crossover so high, since the amp feeding both units is a 3x350w 9ohms (2x600w at 4ohms), isn't it a lot then if the crossover is so high? there's still the passive filter in the 3677 of course

Posted by Demetris Thoupis (Member # 833) on 06-05-2009, 12:15 AM:

You are thinking of using the set as a 3 way! Well unfortunately you can't. It's a two way combination . Mid/Lows combined and Highs seperated. You are actually removing the stress from the 3677 by putting the crossover at 1.8khz. In any case when you bi-amp or tri-amp speakers the high frequency area is really capable of very little wattage. The real watts are needed on the mid and especially the lows. Have you tried the combination I proposed?